You lay comfortably in a lounge chair, perhaps snuggled into a robe of natural fibers, in a quiet, peaceful room. Soothing music plays softly. The cool air is dry and still, and has a slightly salty tinge. For you're relaxing in a salt cave, perhaps in an exclusive modern spa, perhaps deep underground in a real salt mine, undergoing halotherapy or speleotherapy or salt therapy. The room is entirely made of salt, but most spas use machines that grind up salt into fine particles and waft it into the air. The claim is that restful breathing in this environment brings health benefits unavailable in any other conditions. Now, don't ask too quickly exactly what the benefits are supposed to be, or exactly what the specific environmental conditions need to be, because those aren't really too clear. Instead, let's just ask why people all over the world are turning to salt therapy.

So just for grins, I did a Google search for "salt cave therapy". Here are a few specific claims for what conditions salt caves treat, from the first page of Google results. They come from boutique spas selling the service:

Asthma

Allergies

Arthritis

Bronchitis

Chronic obstructive pulmonary disease

Circulatory issues

Cystic Fibrosis

Depression

Digestive problems

Ear infections

Eczema

Fatigue

Hay fever

Immune deficiencies

Inflammation

Migraines

Poor concentration

Post-operative recovery

Psoriasis

Rashes

Rhinitis

Sinusitis

Sleep disorders

Snoring

Stress/anxiety

Smokers cough

Tonsillitis

Viral infections

A small minority of spa sites I reviewed stated that salt caves do not treat any medical conditions, and merely provide relaxation. However, the majority are very clear that their service is a miracle treatment, even a cure, for most or all of these conditions. Clearly the salt cave industry has not yet reached any consensus on exactly what it's selling.

Some of the sites I reviewed emphasized purity of the salt, while others credited all the many minerals in it. One site said that the unique combination of 94 (!) elements in natural salt is what makes it work. A number of sites say all 84 are needed. Another says that they only use Himalayan pink crystal salt, because that's the only way to insure purity (pink salts are pink because they are contaminated with iron oxide). Analyses of Himalayan pink salt have found that it contains between 95-98% salt, with most of the rest being gypsum. Trace elements of about 10 minerals are usually found. Although gypsum is recommended in some alternative medicine schemes, no sound medical research has ever found any benefit from consuming it; so it's not clear why salt therapy practitioners recommend it. Either way, the practice seems to present no clear consensus on whether pure salt or contaminated salt is best; it seems to be a pretty even split. But both sides sound pretty adamant that their way is best.

The mechanism for how salt caves treat these conditions is also in hot dispute. While about half emphasize the salt itself being beneficial once it gets into your lungs, the other half are all about ions. Ions, they say, promote good health. An ion is a molecule with an electric charge, either positive or negative, made so because it has more electrons than protons, or more protons than electrons. Negative ion generators have been a staple of alternative therapies for a long time, based largely on the sciencey-soundingness of the term and a misunderstanding of what they actually do. Negative ion generators use high voltage to add an electron to particles in the air. Electrostatic attraction then causes those particles to move toward, and bind to, a grounded surface such as a wall. Thus, an ionizer can help to reduce the amount of dust particles, allergens, and other particles from the air in a room.

Many of the salt therapy spas claim that the ionizers in their caves produce negative ions that destroy bacteria. This is also wrong. An ionizer can help draw bacteria out of the air, as just described, but it doesn't hurt the bacteria. To kill bacteria, you need not negative ions, but ozone, which consists of three oxygen atoms, O3. Unfortunately, when the ozone concentration is high enough to kill bacteria, it's also toxic to humans. You could never put an ozone generator into a salt cave without damaging the lungs of, or killing, the people inside. So this very basic claim, repeated by the majority of the salt cave spas that I reviewed, is factually wrong. Salt caves, with or without negative ion generators, have no significant effect on bacteria.

Here's an example of some of the ion-related nonsense that I read:

Our cells can only absorb those elements that occur in an ional form. Only under considerable pressure can the elements be transformed into a specific size, making them ional, which enables them to pass through our cell walls.

There is, literally, not a single phrase in there that's correct; not to mention the fact that "ional" isn't even a word. This aptly illustrates what I see as the biggest problem with salt caves and halotherapy in general: it misuses sciencey-sounding language to impress and trick the innocent, scientifically-illiterate public into buying something that's already available for free to everyone: simple relaxation. These salt spas may not be able to agree on the pseudoscientific claims they parrot to peddle their wares, but they do have a few things in common: comfortable recliners, soft music, and warm, dim lighting.

Relaxation is one of the most accessible health remedies on the planet. Relaxation reduces stress, and stress is hard on the body. It's hard on you psychologically, and it's hard on your body physically. Stress, as we've discussed in a number of episodes previously, produces tangible detrimental effects on your body. It contributes to high blood pressure, fatigue, hypertension, anxiety, irritability, and social problems. Simply taking time to relax, be it through exercise, resting, a massage, or just laying on your couch, is good for your health. There is no medical debate on this point. Every doctor would agree, and probably every salt spa owner would even agree. Going to a restful salt spa is good for your health, but it's got nothing to do with the salt, and you could get exactly the same benefit for free by just taking a few minutes to relax anywhere. There is no need to make up random pseudoscience to justify this.

My take is that the majority of salt spa operators, and sellers of salt therapy items, honestly believe that their salt is doing something and is a worthy product. They've been given bad information, and the average person has been offered very little reason to doubt the pervasive pseudoscience that's everywhere. Their sales pitch is justified by the fact that the customers (by and large) have a very nice experience, so it's a cycle that's just going to repeat itself. It's sad because those customers' money could be much better spent, or even better, saved.

Sometimes it gets more serious. In 2013, Julia Medew, health editor for Australia's The Age newspaper, interviewed a David Lindsay, the CEO of a chain of salt therapy spas. He refers to his locations as "clinics" — which strikes me as a deceptive misuse of the word — and said they were planning to expand from three locations to 100 due to their popularity. He claimed that they received medical referrals from both the Royal Children's Hospital and Monash Medical Centre. Medew contacted both hospitals to verify the referrals, but was told by both hospitals that they do not refer patients to Lindsay's company or to any other "non-evidence-based" therapy. Moreover, the Head of Immunology and Allergy at the Royal Melbourne Hospital Professor Jo Douglass told Medew that salt caves are actually dangerous for asthma sufferers, as the salt could trigger narrowing of the airways and an asthma attack. That little factoid is not something I found being marketed on any of the websites.

But I did find these:

After 3 years of research, we learned that all life forms come from a water and salt concentration called sole ("so-lay").

And yet:

The body recognizes table salt as an aggressive cellular poison. It is an unnatural substance, and the body wants to eliminate it as quickly as possible to protect itself.

Despite the following:

A salt crystal manifests a superior structure. Due to this sublime form, the elements are biochemically available for our cells as are the individual frequencies or vibration patterns.

And:

Negative ions are odorless, tasteless, and invisible molecules that we inhale in abundance in certain environments, such as mountains, waterfalls and beaches.

Therefore:

Even the skeptics of the traditional medical fields are swaying toward the probability that this treatment is more than folklore or fable.

Not yet.

Halotherapy has been researched, and the results have been published. A quick search on PubMed (an online index of published research, in virtually every field, including both good research and bad research) reveals 17 articles. 16 of them are in Russian. All 16 of them found positive results, but none were published in peer-reviewed English language journals. This constitutes a pair of red flags. Russia is notorious for its promotion of alternative medicine, and for having virtually no standard of care. That lonely 17th article was published in 2012 in the journal Allergy and Asthma Proceedings, and is titled "Unproved and controversial methods and theories in allergy-immunology". A snippet from its abstract:

Unproved methods and controversial theories in the diagnosis and management of allergy-immunology are those that lack scientific credibility... Unproven treatments and intervention methods for allergic-immunologic conditions include acupuncture, homeopathy, halotherapy, and autologous urine injections.

Any treatment that ranks on a par with urine injections should, in my humble opinion, be regarded with skepticism. The red flags you should note are that there is no standard on what salt therapy is, how it works, or what it does; certainly no standards for how it should be administered. This is because it's a made-up practice; it is not the result of testing or any kind of therapeutic development process. No studies confirming efficacy have been published, at least not in the West; and when we see a subject with no studies at all published (either positive or negative), the reason is usually because there is no coherent theory to test.

Never underestimate the value of good relaxation, and only get your relaxation in a nice salt cave themed boutique spa if it's free.